The present invention relates to centrifugal clutches for transmitting a torque between a driving element and a driven element. Conventionally, these types of clutches employ a casing which encloses a rotor with a pseudo-fluid or granular material disposed therebetween. This material serves to provide the connection between the casing and the rotor. In operation, when the drive member is rotated, it drives the casing of the clutch and by reason of this drive tends to distribute the transmission element, (i.e., granular mass), to the periphery of the casing. By the effect of friction acting in the volumetric area between the rotor and the confronting surfaces of the casing, the rotor is rotated, due to the construction of the casing and rotor, and the circulation of the granular mass in the volumetric space between the rotor and casing. Accordingly, heat released by friction is directed toward the casing and is thereafter removed to the outside through fins provided on the casing.
Centrifugal clutches utilizing a granular or pseudo-fluid material between a rotor and casing have heretofore been in use, and one of such clutches is shown in U.S. Pat. No. 3,460,658, issued Aug. 12, 1969 for Centrifugal Fluid-Powder Clutch with Radial Grooves, but a problem in using such clutches has been the difficulty of dissipating the heat which is built up in the normal use of the clutch. Such heat results from movement under pressure of the pseudo-fluid material with reference to the casing and rotor, and such movement is dependent upon the shape of the grooves in the rotor and casing respectively. The structure in the aforesaid U.S. Pat. No. 3,460,658 utilizes fan shaped grooves in the rotor with similarly shaped grooves in the casing, but such shape of grooves restricted the flow of material, limited the volume of pseudo-fluid material which could be used in the casing to about 75% of the volume of the casing and did not allow prolonged slipping to take place, because the heat released by friction between the material and the casing could not be dissipated. Moreover, such differences in volume results in less power transmitted and an increase in the breakaway torque.